This application claims priority under 35 U.S.C. §119(a) on Japanese Patent Application No. 2007-039797 filed in Japan on Feb. 20, 2007, the entire contents of which are hereby incorporated by reference.
The present invention relates to a document reading apparatus provided with an optical scanning unit that moves back and forth in a document reading direction so as to read information of a document placed on a document placement table arranged in a top face of a frame by irradiating the document with light emitted from a light source lamp, and a distribution cable connected to the light source lamp, and in particular, to a structure supporting the distribution cable.
As schematically shown in FIG. 14, a conventional document reading apparatus is provided with an optical scanning unit 600 that moves back and forth in a document reading direction (hereinafter also referred to as a “sub-scanning direction”) X so as to read information of a document placed on a document placement table arranged in a top face of a frame 500 by irradiating the document with light emitted from a light source lamp 602, and a distribution cable 650 that connects a drive circuit board 510 disposed in a lower portion of the frame 500 and the light source lamp 602. The distribution cable 650 is led out from one end portion in a main-scanning direction Y perpendicular to the sub-scanning direction X of the optical scanning unit 600 (the end portion on the near side in FIG. 14) along the main-scanning direction Y (for example, see JP H2-101863A).
In such a document reading apparatus, as shown partially enlarged in FIG. 15, a support member 610 that supports the distribution cable 650 is provided at a lead-out portion 601 at one end portion of the optical scanning unit 600.
This support member 610 includes a pass-through channel 611 through which the distribution cable 650 led out from the optical scanning unit 600 is passed, with a lead-in opening 612 and a lead-out opening 613 of the pass-through channel 611 being disposed shifted from each other in the main-scanning direction Y. In other words, when viewed from above, the pass-through channel 611 is gently bent in a substantially S shape, and is disposed such that the distribution cable 650 led out from the lead-out portion 601 of the optical scanning unit 600 is slightly pushed inward. This is because in this structure, the distribution cable 650 cannot be led out straight from the lead-out portion 601 for a reason such as dimensional restrictions in design due to downsizing of the document reading apparatus or the like.
In this case, the top portion of the pass-through channel 611 of the support member 610 is open such that the distribution cable 650 can be fitted in easily, for example. For this reason, a pushing plate 614 for preventing uplifting is provided extended in the top portion of the pass-through channel 611 from one of the sides that form the pass-through channel 611, such that the distribution cable 650 fitted in from above is not uplifted from the pass-through channel 611.
With the support member 610 configured as described above, movement of the distribution cable 650 in a lateral direction, that is the main-scanning direction Y, is restricted only at two locations, the lead-in opening 612 and the lead-out direction 613, and the movement in the main-scanning direction Y is not particularly restricted inside the pass-through channel 611. Furthermore, this distribution cable 650 is a parallel duplex cable having a substantially eyeglasses-shaped cross section. The distribution cable 650 is led out from the lead-out portion 601 of the optical scanning unit 600 in a vertical state in which two cores thereof are arranged up and down, is passed through from the lead-in opening 612 of the support member 610 in the vertical state, is twisted so as to be rotated for 90 degrees inside the pass-through channel 610, and then is led out from the lead-out opening 613 in a horizontal state in which the two cores thereof are arranged right and left.
Therefore, under the action of restoring stress that is produced as a result of the distribution cable 650 being supported in substantially an S shape by supporting the distribution cable 650 at two locations, the lead-in opening 612 and the lead-out opening 613, which are disposed shifted from each other in the main-scanning direction Y, and rotational stress to eliminate the twist for 90 degrees inside the pass-through channel 611, the distribution cable 650 led out from the lead-out opening 613 results in being led out to a direction X′, which is slightly inclined to the central portion with respect to the sub-scanning direction X, as shown in FIG. 15.
On the other hand, as shown in FIG. 14, in the vicinity of the inner side of the distribution cable 650, a drive wire 520 for moving the optical scanning unit 600 back and forth in the sub-scanning direction X is disposed parallel to the distribution cable 650. Therefore, when the distribution cable 650 is led out obliquely, it is possible that the distribution cable 650 contacts the drive wire 520 due to back and forth movement of the optical scanning unit 600 in the sub-scanning direction X, a leakage current is generated via floating capacitance present between the distribution cable 650 and the drive wire, and consequently the light intensity of the lamp becomes unstable, or in some cases it is possible that the distribution cable 650 is broken as a result of the coating thereof being damaged due to a frictional force produced between the distribution cable 650 and a pulley holding member 671. In addition, it has been also possible that the optical scanning unit 600 does not operate smoothly due to a frictional force produced between the distribution cable 650 and the drive wire 520 so that the read document image becomes blurred.